1. Field of the Invention
The present invention relates to a method of the continuous measurement of variations in the overall fluid saturation of a porous material sample subjected to drainage or to an imbibition phase, according to the principle of a continuous constant-volume weighing, and to a device for the implementation thereof.
The method according to the invention is notably suited for the study of geologic samples taken in formations containing or likely to contain petroleum effluents.
2. Description of the Prior Art
The knowledge that can be acquired concerning various petrophysical parameters of rocks during drainage or imbibition phases can be used for example for selecting the most appropriate fluid for displacing the petroleum effluents they contain and for improving thereby the efficiency of effluent enhanced recovery processes in a reservoir.
It is known to determine for example the saturation and the wettability of rocks with respect to fluids such as water (in the form of brine) and oil that can be contained therein. To that effect, rock drainage phases are carried out, i.e. a displacement of the fluids intended to decrease the water saturation, followed by imbibition phases which, on the contrary, are intended to increase its water saturation (Sw). The capillary pressure at a point of a porous sample in the presence of water and of oil in the continuous phase is defined, as it is well-known, as the difference Pc at equilibrium between the pressure P(oil) and the pressure P(water). Devices allowing petrophysical parameters of rocks to be measured are for example described in patent applications FR-2,603,040, EN-93/09,481 or EN-94/10,783 filed by the assignee or in U.S. Pat. Nos. 4,868,751 and 5,069,065.